1. Field of the Invention
This invention relates generally to pressure responsive electric switches and more specifically to such switches particularly useful with vehicular transmissions.
2. Brief Description of the Prior Art
It is known to place pressure responsive electric switches in pressure receiving communication with hydraulic fluid in the solenoid valve assembly of a motor vehicle as a way to confirm that solenoid valve actuation and deactuation has occurred. The pressure change associated with valve actuation and deactuation can be sensed using snap acting pressure responsive switches which close or open electric circuits such as those shown in U.S. Pat. No. 4,861,953, assigned to the assignee of the present invention. In that patent, a switch assembly is shown comprising a plurality of electrical conductors overmolded with electrically insulating material and with portions of the conductors left exposed to serve as connector pins, annular disc seats and spring connectors. Runners connecting the several conductors for purposes of maintaining the conductors in a selected spatial relationship with one another during the handling and molding procedure are severed after completion of molding through apertures in the overmolded insulating material aligned with the runners. The annular disc seats are exposed on one side and supported by the insulating material on the opposite side with a stationary contact receiving bore provided through the insulating material at the center of each disc seat. An electrically conductive rivet is received in each stationary contact receiving bore and is positioned along the longitudinal axis of the bore so that an electrically conductive, snap acting disc received on the disc seat is adapted to move into and out of engagement with an end of the rivet. The disc is captured on the disc seat by a sleeve assembly which in turn is adapted to be placed in communication with a pressure source used to actuate the transmission solenoid valves.
In U.S. Pat. No. 5,015,808, also assigned to the assignee of the present invention, a plurality of discrete, modular pressure switches are mounted on a circuit board which is adapted to be secured to a hydraulic manifold such as a valve body whereby the upper surface of each pressure responsive switch abuts and is in sealing relationship with a variable pressure source in the valve body whereby such pressure causes each switch to actuate in accordance with the level of pressure then present at each switch. Use of discrete, modular switches provide an advantage of using the same switches for a number of different specific applications merely by providing an appropriate circuit board layout. However, for some applications, particularly those involving a large number of pressure switch manifold assemblies, it would be desirable to have an assembly which requires fewer connections to make and parts to assemble and which, generally, is less expensive yet inherently more reliable.